title: Altered GABAA receptor expression and seizure threshold following acute ethanol challenge in mice lacking the RIIβ subunit of PKA.
abstract: Ethanol causes pathological changes in GABAA receptor trafficking and function. These changes are mediated in part by ethanol activation of protein kinase A (PKA). The current study investigated the expression of the GABAA α1 and α4 subunits and the kinase anchoring protein AKAP150, as well as bicuculline-induced seizure threshold, at baseline and following acute injection of ethanol (3.5 g/kg IP) in a mouse line lacking the regulatory RIIβ subunit of PKA. Whole cerebral cortices were harvested at baseline, 1 h, or 46 h following injection of ethanol or saline and subjected to fractionation and western blot analysis. Knockout (RIIβ-/-) mice had similar baseline levels of PKA RIIα and GABAA α1 and α4 subunits compared to wild type (RIIβ+/+) littermates, but had deficits in AKAP150. GABAA α1 subunit levels were decreased in the P2 fraction of RIIβ-/-, but not RIIβ+/+, mice following 1 h ethanol, an effect that was driven by decreased α1 expression in the synaptic fraction. GABAA α4 subunits in the P2 fraction were not affected by 1 h ethanol; however, synaptic α4 subunit expression was increased in RIIβ+/+, but not RIIβ-/- mice, while extrasynaptic α4 and δ subunit expression were decreased in RIIβ-/-, but not RIIβ+/+ mice. Finally, RIIβ knockout was protective against bicuculline-induced seizure susceptibility. Overall, the results suggest that PKA has differential roles in regulating GABAA receptor subunits. PKA may protect against ethanol-induced deficits in synaptic α1 and extrasynaptic α4 receptors, but may facilitate the increase of synaptic α4 receptors.
authors.affiliation: Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Carlson
authors.forename: Todd K
authors.initials: TK
authors.lastname: O'Buckley
authors.forename: Rhiannon
authors.initials: R
authors.lastname: Thomas
authors.forename: Todd E
authors.initials: TE
authors.lastname: Thiele
authors.forename: A Leslie
authors.initials: AL
authors.lastname: Morrow
mesh_terms: D000818:Animals; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit / Q000172:deficiency*; D000431:Ethanol / Q000008:administration & dosage*; D005786:Gene Expression Regulation; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011963:Receptors, GABA-A / Q000096:biosynthesis*; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism*
chemical_list: D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D011963:Receptors, GABA-A; D000431:Ethanol